What about talking to the people at wakulima market? They are also serious brokers and will collect the goods from the farm.

Wakulima market is in Nairobi. It is down Haille selasie avenue next to KFA and KGGCU. These guys are basically major suppliers of vegetables in Nairobi. They are all brokers so don't feel anything when they bargain with you. The onion trucks are normally parked on the back side of the market. Depending on how many Tons you have/acres that were planted, you should be able to get a good price. There has been a shortage but now it's normalizing.

If you choose to go to Wakulima Market you will need strong shock absorbers. U will be required to pay amongst others for security u didn't ask for and that you may not need. All this is informal I hope the place has changed though.